4-aminomethylbenzoic acid is utilized as a monomer for preparing polymers or as a raw material for producing antiplasmin agents and as a main ingredient of Cetraxate which is used to treat gastric ulcers.
Conventional methods of preparing 4-aminomethylbenzoic acid and its lower alkylester include subjecting methyl 4-formylbenzoate to catalytic reduction using a Raney nickel catalyst in the presence of ammonia or subjecting methyl 4-cyanobenzoic acid to catalytic reduction using a Raney nickel catalyst in the presence of ammonia or reacting methyl 4-chloromethylbenzoate with liquid ammonia.
However these methods are problematic because a large amount of secondary amine (amino-di-4-methylbenzoic acid) is generated and the yield is low, in particular 4-cyanobenzoic acid cannot be easily prepared or the yield is low. Furthermore, because the conventional methods cause high toxicity in terms of the properties and generate pollution, there are required methods of preparing 4-aminomethylbenzoic acid which are associated with low toxicity, no pollution, and high yield.
In order to solve the above problems, patent literature 1 discloses the preparation of 4-aminomethylbenzoic acid or 4-acetylaminobenzoic acid by subjecting 4-carboxybenzaldehyde or its alkylester to oximation thus obtaining an oxime which is then reduced using a nickel catalyst in the presence of ammonia or acetic anhydride.
However the method disclosed in patent literature 1 is problematic because catalytic reduction is carried out in the presence of ammonia or acetic anhydride, acetic acid, etc., and hydrogenation is conducted at a high pressure of 20 atm or more, and thus limitations are imposed on selecting the reactor that can be used, and the purification process is excessively expensive. Moreover, there is a high cost due to high pressure and the work is not consistent.    (Patent Literature 1) Patent Literature 1: Japanese Unexamined Patent Application Publication No. 1981-12350